The path to obesity may begin much earlier than anyone thought, according to a new study that found about a third of U.S. babies were too fat.

In a long-term study of more than 7,500 infants across the country, nearly 32 percent of babies were deemed overweight or even obese at 9 months. By the time the children were 2 years old, that number had nudged up to more than 34 percent.

“It definitely raised eyebrows when we saw how early it was showing up," said Brian Moss, an adjunct professor at Wayne State University and author of new research in the American Journal of Health Promotion.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Experts say the best way to treat chubby babies is to monitor their diets for quality and quantity — particularly portion size.

“It can take just a few tweaks to a baby’s diet to make a difference,” said Dr. Wendy Slusser, an associate clinical professor and medical director of the Fit for Healthy Weight Program at the Matell Children’s Hospital at the University of California, Los Angeles.

“It’s probably only about 150 calories a day difference that we’re talking about.”

Good news? Kids' weight goes down, too
While experts were distressed to see that babies that young were already significantly overweight, they did see a hopeful message in the new study’s details. Some of the chunkiest 9-month-olds had shed their excess pounds by the time they were 2. During the same time frame, however, some of the normal-weight infants had gained too much weight.

“It means that in that age group weight is a lot more fluid than it is in an obese 14-year-old,” said Dr. Goutham Rao, clinical director of the Weight Management and Wellness Center at the Children’s Hospital of Pittsburgh at the University of Pittsburgh Medical Center.

“And that means that these children are not necessarily condemned to be obese,” added Rao, who was not affliated with the new study.

Still, Rao and others warned that parents of the heaviest babies should take heed and make changes as soon as possible. Parents need to figure out what it is about their baby’s diet that is causing weight gain, he said.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

“Every child that has a healthy diet will get to a healthy weight,” Rao said.

The children in the new study were all born in 2001. Weight and height (length in the case of the infants) were measured at 9 months and at 2 years. Then the researchers compared the measurements for the babies in the study to standard growth charts developed by the Centers for Disease Control and Prevention. Those charts were based on measurements gathered between 1963 and 1994.

Kids who were above the 85th percentile for weight compared with height were considered overweight. Children who were above the 95th percentile were considered obese, according to the researchers' definition.

Surprisingly, high birth weight wasn't a reliable indicator of whether a baby would be overweight or obese, experts said. Some big babies thin out quickly, while some babies born small become heavy, sometimes because parents overcompensate with food.

Most concerning in the current study was that 32 percent of the kids born in 2001 fell into the overweight range, more than double the 15 percent of children whose measurements were used to construct the charts.

“This could be a red flag telling us that we need to be aware and to be focusing on healthy eating habits early on,” said Slusser, the UCLA expert.

Stay away from sweet food, drink
The best way to get an infant or toddler’s weight under control is to go back to basics, Rao said. That means staying away from sweet drinks, including fruit juices, and high-fat, high-sugar foods.

“You would be surprised at some of the foods and drinks kids are given,” Rao said. “You see a lot of very young children eating French fries, because that’s what their parents are eating. Sometimes you’ll even see parents putting regular soda into a baby’s bottle.”

Breast-feeding is the healthiest choice, if possible, Slusser said. And when it’s time to introduce solid foods, lean heavily on pureed vegetables and fruits.

One more bit of advice from Rao: Pay close attention to portion sizes.

“Parents often don’t realize that children’s portions are far smaller than those of adults,” he said. “The rule of thumb at our center is that your portion of any sort of food should be no bigger than your fist. For a 1-year-old, that’s pretty tiny.”